The chance to let powerful visible lasers
escape into the open sky is a dream for
every laser engineer—yet having four
of them at the same time ‘imprinting’
impressive columns of light into the
clean air of the desert and aiming at
the Southern Cross constellation was
the visual highlight of a recent event
(see Fig. 1).

On April 26, 2016, the southern skies
witnessed the “first light” of four new
20 W-class sodium guide star lasers
pointing to the stars at the European
Southern Observatory’s (ESO; Garching,
Germany) Paranal Observatory in the
Chilean Atacama desert. 1 With this
event, a seven-year contract and collaboration between laser suppliers Toptica
Photonics (Graefelfing, Germany) and
MPB Communications
(MPBC; Montreal,
QC, Canada), and ESO
as development partner
and customer, comes to
a successful finish.

This first light eventalso marks an import-ant milestone in a ma-jor upgrade of ESO’sVery Large Telescope(VLT) to transform theUnit Telescope 4 into astate-of-the-art adap-tive telescope facility(AOF). 8 The transforma-tion will involve furthersteps: in late 2016 withthe installation of a new

1. 1 m deformable second-ary mirror, and in 2017 with the com-missioning of the two adaptive opticsmodules: GRAALand GALACSI.Adaptive op-tics systems consist-ing of natural and/or artificial guidestars, wavefront sen-sors, real-time com-puters, and deform-able mirrors are themethod of choice tocounteract the im-age-blurring effectsof unavoidable at-mospheric turbulenceat ground-based op-tical telescopes. Infact, even at the best optical sites onEarth such as the 2600 m summit ofCerro Paranal or the 4205 m summitof Mauna Kea in Hawaii, refractive-in-dex variations in the atmosphere lead toa seeing-limited resolution of 0.4 arcsecin contrast to the theoretical diffrac-tion-limited resolution of less than 0.02arcsec for the 8. 2 m VLT telescopes.Since there are not enough bright,natural guide stars in many parts of

Consisting of four individual telescopeswith 8. 2 m primary mirrors, the VeryLarge Telescope’s “first light” is nowquadrupled, thanks to four guidestars working in concert to deliverhigh angular resolution and enhancedadaptive-optics compensation.